C NMR spectra of

C NMR The C NMR spectra of carboxylic acid derivatives like the spectra of carboxylic acids themselves are characterized by a low field resonance for the carbonyl... 

C-nmr data have been recorded and assigned for a great number of hydantoin derivatives (24). As in the case of H-nmr, useful correlations between chemical shifts and electronic parameters have been found. For example, Hammett constants of substituents in the aromatic portion of the molecule correlate weU to chemical shifts of C-5 and C-a in 5-arylmethylenehydantoins (23). Comparison between C-nmr spectra of hydantoins and those of their conjugate bases has been used for the calculation of their piC values (12,25). N-nmr spectra of hydantoins and their thio analogues have been studied (26). The N -nmr chemical shifts show a linear correlation with the frequencies of the N—H stretching vibrations in the infrared spectra. 

The NMR spectrum of quinoxaline has been measured in CDCI3 and the chemical shift values are as shown in (16) (69JA6381). Curiously, C NMR spectra of phenazine and its derivatives have been recorded in benzene solution and the chemical shift values quoted relative to benzene however, for consistency the values in (17) are quoted relative to TMS. 

In contrast to the previous section, there is little information available on C NMR spectra of pyrazoles and indazoles in books or reviews. Consequently, this section will treat the literature results in some detail, giving the principal references and some illustrative examples. 

FIGURE 13.26 C NMR spectra of 1-phenyl-1-pentanone. (a) Normal spectrum, (b) DEPT spectrum recorded using a pulse sequence in which CH3 and CH carbons appear as positive peaks, CH2 carbons as negative peaks, and carbons without any attached hydrogens are nulled. 

Compound A and compound B are isomers having the molecular formula C10H12O. The mass spectrum of each compound contains an abundant peak at nih 105. The C NMR spectra of compound A (Figure 17.23) and compound B (Figure 17.24) are shown. Identify these two isomers. 

Chemical Shifts of the Carbons in the C NMR Spectra of 1,2,4-Triazine V-Oxides IN DMSO- Is IN Comparison ( ) with Those of the Parent 1, 2,4-Triazines... 

Figure 3 C NMR spectra of 1-NBR and 2-3-HNBR with 80 and 99.9 mol% hydrogenation, respectively. Source Ref. 11.

Fig. 13. CP/MAS 13 C NMR spectra of wood from birch (A) and of hydrolyzed birch (B). A contact time of 2 ms and a pulse repetition time of 5 s were used...

It is worth noting, prior to citing actual metal atom studies, the recent secondary ion mass spectrometry (SIMS) on an argon matrix-isolated propene sample, demonstrating the applicability of SIMS analysis to the characterization of matrix-isolated species. The same group h s reported the first C NMR spectra of organic molecules trapped in an argon matrix. ... 

All cyclic compounds of types 83-88 have been characterized by their diagnostically simple and C-NMR spectra. Some general regularities can be observed, namely, a small but steady upfield shift in the C-NMR spectra of the carbon signals of the polyacetylenic macrocycle with increasing ring sizes. 

DEPT (9 = 135° and 90°) and broad-band decoupled C-NMR spectra of ethyl acrylate are shown. Assign the signals to various carbons of the molecule. 

The DEPT and broad-band decoupled C-NMR spectra of vasicinone, C11H10N2O2, isolated from a plant Adhatoda vasica, are shown. Spec-... 

FIG. 14 C NMR spectra of the EPC SUV in the presence and the absence of BPA, at the EPC atom sites of (a) carbonyl, (b) olefinic, (c) choline and glycerol, and (d) methylene and methyl carbons. In each spectral region, the upper trace represents the EPC spectrum before the addition of BPA, while the lower is that after the BPA delivery. Asterisks denote the signals of the reference, DSS. (From Ref. 47. Copyright 1999 American Chemical Society.)... 

The hydrolytic stability of PSPDM was studied initially at 90°C in aqueous solution at pH 1.2 (0.1(1 HC1), pH 7 and pH 12.3 (0.1M NaOH). At both pH 1.2 ay pH 7, no detectable hydrolysis occurred after thirty days. The C NMR spectra of these samples were unchanged. Under acidic and neutral conditions, the hydrolytic stability of the imide was excellent. 

Figure 1. Variation with temperature of the C-NMR spectra of 1-butene adsorbed on NaGeX zeolite (0 = 0.5).

Figure 2. C-NMR spectra of 1-butene (Bj) and cis (B2C) and trans 2-butene (B2t) adsorbed on NaGeX zeolite, at various time intervals during the isomerization reaction. "Reproduced with permission from Ref. 4 Copyright 1981, Academic Press".

Four different experiments were realized by labeling either the methanol or the ethylene molecules (Figure 7). The reactions were studied in static conditions adsorbing either methanol (A and B) or ethylene (C and D) prior to the second reactants. The l C-NMR spectra of Figure 7 reveals that the order of adsorption of the reactants is very important for the reactivities at first, surface alkylation occurs and is followed by separated reaction pathways for CH3OH and C2H/. 

Figure 8. High resolution CP/MA.S solid state C-NMR spectra of tetrapropyl- and tetrabutylammonium ions in ZSM-5 and ZSM-11 zeolites respectively. 11 Reproduced with permission from Ref. 11 Copyright 1981, Butterworth and Co (Publishers) Ltd c ".

Figure 1. 62.9 MHz 13 C NMR spectra of the salt 9b TPFPB in toluene-d8 at 273K ( TPFPB anion, toluene-d8).

Table 11 p-Substituent factors, A, for calculating H- and C-nmr spectra of p-diketones. 

Figure 5 a-CH3 portion of the C-NMR spectra of poly DMAEMA (a) prepared in water/ethanol, (b) prepared in water. 

The H- and C-NMR spectroscopic data support the proposed primary structure of poly(Lys-25). The amide carbonyl resonances are particularly informative as these signals are well resolved in the C-NMR spectrum of poly(Lys-25) (Figure 4). An amide carbonyl resonance is observed at 174.9 ppm for poly(Lys-25) that does not appear in the spectrum of poly(Val-Pro-Gly-Val-Gly) [13]. The position and relative intensity of this resonance are consistent with a lysine amide carbonyl group within a peptide bond [14]. Moreover, the resonances of the amide carbonyl groups for other residues in the pentapeptide repeat are split due to the substitution of a lysine residue at position 4 in every fifth pentapeptide in Lys-25. In addition, the absence of splitting in amide carbonyl group of valine in position 4 (174.5 ppm) supports this assignment, as this residue is replaced by lysine in the fifth pentapeptide of the Lys-25 repeat. The presence of other resonances attributable to the lysine residue can be detected in the H- and C-NMR spectra of the Lys-25 polymer at levels commensurate with its... 

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